Antinociception and modulation of rostral ventromedial medulla neuronal activity by local microinfusion of a cannabinoid receptor agonist
Section snippets
Experimental animals and surgical preparation
All experiments were performed after the review and approval of the Institutional Animal Care and Use Committee at the University of California, San Francisco and carried out in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals. All possible efforts were made to minimize the number of animals used and their suffering. Experiments were conducted using 67 male Sprague–Dawley rats (325–450 g; Bantin and Kingman, Hayward, CA, USA) injected with
Results
The effect of microinfusing vehicle, WIN 55,212–2 and WIN 55,212–2+SR141716A on tail flick latencies and neuronal activity was determined using a total of 67 animals. Neuronal activity and tail flick latencies were recorded for at least 20 min following the completion of each microinfusion. In some experiments, to determine the time-course of the drug effect, data were recorded for 45 min after the microinfusion. Recording sites were located within the RVM, including the nucleus raphe magnus,
Discussion
Previous experiments from this laboratory demonstrated changes in RVM neuronal activity and tail flick latencies following i.v. administration of the cannabinoid receptor agonist, WIN 55,212–2 (Meng et al., 1998). The current study evaluated whether these effects on neuronal activity and tail flick latencies could be mediated by cannabinoid receptors located locally within the RVM. Results from the current study demonstrate that microinfusion of a cannabinoid receptor agonist into the RVM
Acknowledgements
Supported by the U.S. National Institutes of Health (DA 14548 to I.D.M.). We thank Ichiro Harasawa for his critical reading and helpful suggestions.
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